JP6978827B2 - Exhaust gas purification catalyst unit - Google Patents

Description

The present invention relates to an exhaust gas purification catalyst unit, and relates to an exhaust gas purification catalyst unit suitable for improving catalyst efficiency, for example, in a denitration device for removing nitrogen oxides in boiler exhaust gas.

For example, NOx in flue gas emitted from power plants, various factories, automobiles, etc. is a causative substance of photochemical smog and acid rain. As an effective removal method, _{a selective catalytic reduction denitration method using a catalyst using ammonia (NH 3} ) as a reducing agent is widely used mainly in coal-fired power plants.

As the denitration catalyst, a titanium oxide-based catalyst containing vanadium (V), molybdenum (Mo), and tungsten (W) as active ingredients is used. Generally, salts of these active ingredients and titanium oxide or a precursor thereof are kneaded in the presence of water, and the obtained paste is molded into a plate shape or a honeycomb shape, dried and fired. For example, after applying the above-mentioned catalyst component to a net-like substrate obtained by processing a thin metal steel plate into a metal lath, or a woven or non-woven fabric substrate made of ceramic fibers, the linear protrusions and the flat surface portion are molded at predetermined intervals. The plate-shaped catalyst element thus obtained is used. A catalyst unit formed by stacking a plurality of catalyst elements in a rectangular metal frame with linear protrusions as spacers at equal intervals and arranging the linear protrusions so as to be parallel to the gas flow direction has a ventilation pressure loss. It has the characteristic of being small. For this reason, it has features such as being less likely to cause wear due to soot and coal combustion ash and clogging of the flow path, and is currently widely used in exhaust gas treatment equipment for boilers for thermal power generation (for example, No. 1 of Patent Document 1). 1 and FIG. 23 of Patent Document 2).

Further, in such a catalyst unit, the height of the flow path having a rectangular cross section formed by laminating a plurality of catalyst elements can be freely adjusted by changing the height of the spacer of the catalyst element. For example, in the case of high efficiency and compactness, the height of the spacer between the catalyst elements is lowered to increase the number of laminated layers. On the other hand, when the amount of dust in the exhaust gas is large and clogging is prevented, the height of the spacer between the catalyst elements is increased.

Jikkenhei No. 1-88732 Gazette Japanese Unexamined Patent Publication No. 9-10599

By the way, in the catalyst unit described in Patent Documents 1 and 2, one of the upper and lower surfaces of the gas flow path formed between the catalyst element located at the top and bottom of the metal frame and the metal frame surface is the metal frame surface. Therefore, there is a point to be improved that the catalytic action on the exhaust gas to be treated flowing through those gas channels is not sufficient. That is, among the gas flow paths formed between the catalyst elements arranged in layers in the catalyst unit, the gas flow paths formed between the catalyst element at the top and bottom and the metal frame surface are on the upper and lower surfaces. One is the catalyst surface, the other is the metal frame surface, and about half of the gas flow path is occupied by the metal frame surface. Since the metal frame surface is inactive with respect to the exhaust gas to be treated, the catalytic performance of these gas flow paths is lower than that of other gas flow paths whose upper and lower surfaces are formed by the catalytic surface. Further, since the number of spacers of the catalyst element in contact with the metal frame surfaces at the top and bottom is approximately half, the cross-sectional area of the gas flow paths at the top and bottom is larger than that of the other flow paths, so that the ventilation resistance is low. Therefore, since the amount of gas that blows through without reacting increases, there is a point to be improved that the catalyst performance of the catalyst unit as a whole cannot be sufficiently exhibited.

The problem to be solved by the present invention is to promote the catalytic reaction of the gas flow path formed in the upper part and the bottom of the conventional catalyst unit with the exhaust gas to be treated, and to reduce the amount of gas that blows through without reacting, so that the whole is solved. It is to provide a catalyst unit for exhaust gas purification which can improve exhaust gas purification performance.

In order to solve the above problems, the present invention presents a catalyst element having a plurality of spacers composed of linear protrusions on both sides of a plate-shaped catalyst, and a metal frame having a rectangular cross section having gas inlet and gas outlet openings at both ends. The catalyst element is located in the linear direction of the spacer from the upper part to the lower part of the metal frame in the gas flow direction, and a plurality of the catalyst elements are stacked and housed in a layered manner. The frame surface has a gas stirring protrusion composed of linear protrusions protruding toward the catalyst element facing the frame surface, and the gas stirring protrusion is in a direction intersecting the extension direction of the spacer of the catalyst element. We propose a growing catalyst unit for exhaust gas purification.

According to the present invention configured as described above, the exhaust gas to be purified flowing into the gas flow path formed between the catalyst element at the top and bottom of the catalyst unit and the metal frame surface protrudes into the gas flow path. The gas flow is agitated by colliding with the gas agitating protrusion. By the stirring, the exhaust gas flowing in the vicinity of the metal frame surface can also come into contact with the catalyst element on the opposite side constituting the gas flow path to promote the catalytic reaction. As a result, the overall exhaust gas purification performance can be improved.

In the exhaust gas purification catalyst unit of the present invention, the following aspects may be appropriately adopted.
(1) The spacer is composed of a pair of mountain-shaped protrusions protruding from one surface and valley-shaped protrusions protruding from the other surface.
(2) The pair of the mountain-shaped protrusions and the valley-shaped protrusions must be continuously located.
(3) The gas stirring protrusion is located so as to face the flat surface between the spacers of the two adjacent catalyst elements.
_{(4) The distance P 1 in} the stacking direction of the catalyst elements is a value selected from the range of 4 [mm] to 10 [mm], and the height H of the second linear projection is H / P. the value of ₁ of the ratio is set in the range of 1 / 3-2 / 3.
(5) A plurality of the gas stirring protrusions are provided in the gas flow direction, and the installation interval D thereof is set to a value selected from the range of 20 [mm] to 50 [mm].
(6) The metal frame is made of rolled steel plate having nominal dimensions close to a thickness of 1 [mm] to 2 [mm].

According to the present invention, it is possible to promote the catalytic reaction of the gas flow path formed at the top and bottom of the conventional catalyst unit with respect to the exhaust gas to be treated, and to improve the overall exhaust gas purification performance.

It is a front view seen from the gas inlet of one Embodiment of the exhaust gas purification catalyst unit of this invention. It is a perspective view of the catalyst element of one Embodiment of this invention. It is a perspective view seen from the gas inlet of one Embodiment of this invention. It is a perspective view which looked at the metal frame of one Embodiment of this invention from a gas inflow port. It is a perspective view of the gas stirring protrusion provided on the frame surface of the bottom of the metal frame of one Embodiment of this invention. It is sectional drawing explaining the operation of the gas stirring protrusion of one Embodiment of this invention.

An embodiment of the exhaust gas purification catalyst unit of the present invention will be described with reference to FIGS. 1 to 6. The present embodiment is an example of applying the present invention to an exhaust gas purification catalyst unit used mainly for removing nitrogen oxides (NOx) in the exhaust gas of a coal-fired boiler. However, the present invention is not limited to coal-fired boilers, and can be applied to exhaust gas purification catalyst units used for removing harmful substances from various boiler exhaust gases such as gas-fired, heavy oil-fired, and crude oil-fired. Further, it is needless to say that the present invention is not limited to the removal of nitrogen oxides (NOx) and can be applied to an exhaust gas purification catalyst unit used for removing various harmful substances.

As shown in FIG. 1, the exhaust gas purification catalyst unit (hereinafter, simply referred to as a catalyst unit) 10 of the present embodiment includes a plate-shaped catalyst element 1 and gas inlets and gas outlets at both ends. It is configured to include a metal frame 4 having a rectangular cross section having an opening of. As described in the column of the prior art, the catalyst element 1 uses, for example, a titanium oxide-based catalyst containing vanadium (V), molybdenum (Mo), and tungsten (W) as active ingredients. Salts of these active ingredients and titanium oxide or a precursor thereof are kneaded in the presence of water, and the obtained paste is molded into a plate shape, dried and fired. Further, in order to mold into a plate shape, for example, a net-like substrate obtained by processing a thin metal steel plate into a metal lath, or a woven or non-woven fabric substrate made of ceramic fiber is formed by applying the above-mentioned catalyst component. Further, in the catalyst element 1, a plurality of linear projection spacers 2 are formed on both sides of the catalyst element 1 in order to stack the plurality of catalyst elements 1 in layers at intervals and accommodate them in the metal frame 4. Has been done.

As shown in FIG. 2, the catalyst element 1 is obtained by molding the spacer 2 and the flat surface 3 at predetermined intervals (for example, 126 mm). The spacer 2 is composed of a pair of mountain-shaped protrusions 2a protruding from one surface (front surface) and valley-shaped protrusions 2b protruding from the other surface (back surface). The protrusions 2a and 2b are continuously positioned to form the spacer 2. The spacer 2 is housed in the metal frame 4 by extending the linear direction in the gas flow direction. Further, as shown in FIGS. 1 and 3, a plurality of catalyst elements 1 are stacked in a layered manner via the spacer 2 and housed in the metal frame 4. The two catalyst elements 1 adjacent to each other in the vertical direction are formed so that the spacer 2 is located at the center of the flat surface 3 on the opposite side.

The metal frame 4 is formed by using a plate material having good malleability and easy processing. In this embodiment, it is formed by using a rolled steel material for a general structure (for example, SS400). However, the material used for the metal frame 4 is not limited to this, and a rolled stainless steel material (for example, SUS430) may be used. Further, for the thickness of the plate material forming the metal frame 4, it is preferable to select a plate material having a nominal size close to about 1 to 2 [mm], which is excellent in workability and easy to handle.

Next, an embodiment of the gas stirring protrusion 6, which is a feature of the present invention, will be described with reference to FIGS. 1, 4 and 5. On the upper frame surface 4a and the bottom frame surface 4b of the metal frame 4 of the present embodiment, gas stirring protrusions 6 composed of linear protrusions protruding toward the catalyst element 1 facing the frame surfaces 4a and 4b, respectively, are provided. It is formed.

As shown in FIGS. 1 and 4, the gas stirring protrusion 6 is formed by extending in a direction intersecting the extending direction of the spacer 2 of the linear protrusion of the catalyst element 1 (in the illustrated example, a direction orthogonal to or substantially orthogonal to the extending direction). Has been done. Further, a plurality of gas stirring protrusions 6 are provided at intervals in the gas flow direction. In the gas stirring protrusion 6 of the present embodiment, in the process of forming the catalyst element 1, a part of the metal frame 4 is recessed in a streak using a press machine equipped with a predetermined mold, and a protrusion is formed on the opposite side. Form. The present invention is not limited to this, and linear protrusions having predetermined dimensions may be formed as gas stirring protrusions 6 by adhering them to the frame surface 4a or 4b of the metal frame 4. As in the former case, it is preferable to form the product using a press machine because it is easy to manufacture and the weight can be reduced.

According to the exhaust gas purification catalyst unit of the present embodiment described above, the gas to be treated 8 flows into the catalyst unit 10 from the direction of the arrow shown in FIG. 1, and the catalyst elements 1 at the top and bottom and the metal frame surfaces 4a and 4b It flows into the gas flow path formed between the two. As a result, as shown in FIG. 6, the gas flow is agitated as shown by an arrow in the figure by colliding with the gas agitating protrusion 6 protruding into the gas flow path. By the stirring, the exhaust gas flowing in the vicinity of the metal frame surfaces 4a and 4b can also come into contact with the catalyst element 1 on the opposite side constituting the gas flow path to promote the catalytic reaction. As a result, the overall exhaust gas purification performance can be improved.

Next, the relationship between the height H, the width W, and the interval D in the gas flow direction of the gas stirring protrusion 6 will be described. Here, the spacing in the stacking direction of the catalyst elements 1 is P _1, and the spacing in the rowing direction of the spacers 2 is P ₂ . In particular, the shape and arrangement of the gas stirring protrusion 6 is preferably determined so as to satisfy the following requirements.
(1) It is desirable that the height H of the gas stirring protrusion 6 is set so that the value of the ratio of _{H / P 1 is in the range of 1/3 to 2/3.}
(2) The interval D of the gas stirring protrusions 6 in the gas flow direction is preferably in the range of 20 [mm] to 50 [mm]. If the interval D is too wide, the effect of stirring the gas will not be sustained and the effect will be small. On the other hand, the narrower the interval D, the greater the effect, but if it is too narrow, when the metal frame 4 is pressed to form streak protrusions, the metal frame 4 is distorted or the pressure loss becomes too high. Not preferred. Therefore, it is preferable to set the interval D in consideration of the plate thickness of the metal frame 4.
(3) The cross-sectional shape of the gas stirring protrusion 6 along the flow direction is preferably a mountain shape or a wide shape of valleys because the gas in the flow path can be efficiently agitated. However, a semicircular shape is also acceptable.
(4) Let A be the cross-sectional area of the gas flow path formed by being surrounded by the two spacers 2, the frame surfaces 2a and 2b, and the flat surface 3 of the catalyst element 1, and the projection seen from the gas flow direction of the gas stirring projection 6. When the area is S, it is preferable to set the width W of the gas stirring projection 6 so that the ratio of S / A is 20% to 60%. If this ratio S / A is set to 40% to 60%, the diffusion effect of the gas can be enhanced and the catalytic reaction efficiency can be enhanced, which is desirable. That is, if the ratio S / A exceeds 60%, the ventilation pressure loss of the gas flow path increases with respect to the improvement of the catalytic reaction due to the stirring effect, which is not desirable.

Next, using the exhaust gas purification catalyst unit of the present invention shown in the above embodiment, Examples 1 to 6 and Comparative Examples 1 to 5 in which the shape dimensions H and W of the gas stirring protrusions 6 and the interval D are changed are performed. The denitration reaction rate ratio and the ventilation pressure loss will be described in comparison.

The method for manufacturing the catalyst element 1 common to Examples 1 to 7 will be described. Mixed ammonium titanium dioxide 10kg and molybdate _{((NH 4) 6 · Mo} 7 O 24 · 4H 2 O) to 1 kg, ammonium metavanadate 1 kg, and an oxalic acid 1 kg, 1 hour kneader while adding water, kneaded And put it in a paste state. Then, 2 kg of silica-alumina-based inorganic fiber was added and kneaded for another 30 minutes to obtain a catalyst paste having a water content of about 30%. The obtained paste was applied to the gaps and the surface of a stainless steel metal lath substrate having a width of 500 mm previously prepared using a pair of rolling rollers to obtain a strip-shaped catalyst having a thickness of about 0.7 mm. _{A corrugated spacer (height P 1} = 5 [mm], installation interval P ₂ = 126 [mm]) was formed therein using a press machine as shown in FIG. 2, and the catalyst element 1 was manufactured.

Separately from the production of the catalyst element 1, a plurality of gas stirring protrusions 6 shown in FIG. 5 are formed by using a press machine in which a mold is installed in a part of a rolled steel material SS400 having a thickness of 2 mm, and then the rectangular shape shown in FIG. 4 is formed. The metal frame 4 was formed. The plate-shaped catalyst elements 1 were stacked and housed in the metal frame 4 in a layered manner, and then air-dried for 24 hours and then fired at 500 ° C. for 2 hours while flowing air to manufacture the catalyst unit 10.

[Example 1]
The gas stirring protrusion 6 of Example 1 has a height H = 2.5 [mm], a width W = 100 [mm}, and an interval D = 30 [mm], and gas stirring with respect to the cross-sectional area A per gas flow path. The ratio S / A occupied by the projected area S of the protrusion 6 is 40%.

[Example 2]
The catalyst unit 10 was manufactured in the same manner as in Example 1 except that the height of the gas stirring projection 6 of Example 2 was changed to H = 1.7 [mm]. The ratio S / A of the projected area S of the gas stirring projection 6 to the cross-sectional area A per gas flow path is 27%.

[Example 3]
The catalyst unit 10 was manufactured in the same manner as in Example 1 except that the height of the gas stirring projection 6 of Example 3 was changed to H = 3.3 [mm]. The ratio S / A of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this embodiment is 52%.

[Example 4]
The catalyst unit 10 was manufactured in the same manner as in Example 1 except that the gas stirring protrusion 6 of Example 4 was changed to a height H = 3.3 [mm] and a width W = 75 [mm]. The ratio S / A of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this embodiment is 40%.

[Example 5]
For the gas stirring protrusion 6 of Example 5, the catalyst unit 10 was manufactured in the same manner as in Example 1 except that the installation interval was changed to D = 20 [mm]. The ratio S / A of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this embodiment is 40%.

[Example 6]
The catalyst unit 10 was manufactured in the same manner as in Example 1 except that the gas stirring protrusion 6 of Example 6 was changed to the installation interval D = 50 [mm]. The ratio S / A of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this embodiment is 40%.

[Comparative Example 1]
In Comparative Example 1, a conventional catalyst unit was manufactured by using the metal frame 4 in which the gas stirring protrusion 6 was not installed in Example 1.

[Comparative Example 2]
In Comparative Example 2, the catalyst unit was manufactured in the same manner as in Example 1 except that the height of the gas stirring protrusion 6 was changed to H = 5 [mm] in Example 1. The ratio S / A of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this comparative example is 80%.

[Comparative Example 3]
In Comparative Example 3, a catalyst unit was manufactured in the same manner as in Example 1 except that the height H = 1 [mm] and the width W = 110 [mm] of the gas stirring protrusion 6 were changed in Example 1. The ratio S / A of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this comparative example is 18%.

[Comparative Example 4]
In Comparative Example 4, a catalyst unit was manufactured in the same manner as in Example 1 except that the height H = 5 [mm] and the width W = 35 [mm] of the gas stirring protrusion 6 were changed in Example 1. The ratio S / A = 28% of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this comparative example.

[Comparative Example 5]
In Comparative Example 5, a catalyst unit was manufactured in the same manner as in Example 1 except that the distance D of the gas stirring protrusions 6 was changed to 100 [mm] in Example 1. The ratio S / A = 40% of the projected area S of the gas stirring protrusion 6 to the cross-sectional area A per gas flow path of this comparative example.

For the catalyst units manufactured in Examples 1 to 6 and Comparative Examples 1 to 5, the denitration reaction rate and pressure loss were measured under the exhaust gas conditions shown in Table 1. Based on the performance of Comparative Example 1 (= 1.00), Table 2 shows the ratio of the denitration reaction rate and the pressure loss of Examples and Comparative Examples, respectively. From Table 2, the catalyst units of Examples 1 to 6 in which the gas stirring protrusion 6 is installed within the range specified by the present invention have a higher denitration reaction rate than the catalyst unit of Comparative Example 1 in which the gas stirring protrusion is not installed. It turns out to be expensive.

On the other hand, in Comparative Examples 2, 3 and 5, when the width W of the gas stirring protrusion 6 was wide, the height H of the gas stirring protrusion 6 was increased so as to come into contact with the facing catalyst element 1 as in Comparative Example 2. In this case, the reaction rate is improved, but the degree of increase in pressure loss is too large. On the other hand, when the height H of the gas stirring protrusion 6 is low as in Comparative Example 3 or when the installation interval D of the gas stirring protrusions 6 is too wide as in Comparative Example 5, the stirring effect of the gas in the flow path is small. Therefore, no improvement in reaction rate is seen.

Further, in Comparative Example 4, the reaction rate is lower than that of Example 2 even though the ratio of the projected area S of the gas stirring projection 6 to the flow path cross-sectional area A is almost the same as that of Example 2. .. This is probably because, in the case of Comparative Example 4, the gas in the flow path has passed through both sides of the gas stirring protrusion 6. On the other hand, in the case of the second embodiment, the width W of the gas stirring protrusion 6 is wide, and there is an appropriate space between the gas stirring protrusion 6 and the catalyst element 1 facing the gas stirring protrusion 6, so that the frame surface of the metal frame 4 is formed. It is considered that the contact reaction between the exhaust gas and the catalyst element 1 is efficiently proceeding because the gas flowing in the vicinity of 4a and 4b can move toward the facing catalyst element 1.

Although the present invention has been described above based on one embodiment, the present invention is not limited thereto. It is obvious to those skilled in the art that it is possible to carry out in a modified or modified form within the scope of the present invention. It goes without saying that such modified or modified forms fall within the scope of the claims of the present application.

In particular, according to the present invention, the denitration performance with the same catalyst amount (same catalyst volume) can be improved, so that the amount of catalyst used can be reduced. Further, since the installation conditions of the gas stirring protrusions to be installed in the metal frame can be freely set according to the exhaust gas conditions of the actual machine, it is possible to correspond to a wide range of exhaust gas conditions.

Further, any catalyst unit formed by laminating plate-shaped catalyst elements can be applied to all catalyst units having different harmful substances to be purified. In particular, in the case of a catalyst unit having a large stacking pitch of catalyst elements, the gas flow path having a low catalytic reaction occupies a large proportion, so that the application effect of the present invention is large.

As described above, the present invention can increase the denitration reaction activity while keeping the increase in ventilation loss of the catalyst unit low.

1 Catalyst element 2 Spacer 2a Mountain-shaped protrusion 2b Valley-shaped protrusion 3 Flat surface 4 Metal frame 4a Upper frame surface 4b Lower frame surface 5 Catalyst unit 6 Gas stirring protrusion 7 Catalyst unit 8 Processed gas inflow direction

Claims (6)

A catalyst element having a plurality of spacers composed of linear protrusions on both sides of a plate-shaped catalyst and a metal frame having a rectangular cross section having openings for a gas inlet and a gas outlet at both ends are provided, and the catalyst element is the metal frame. The spacer is located in the gas flow direction from the top to the bottom in the linear direction of the spacer, and a plurality of the spacers are stacked and accommodated in a layered manner. The catalyst elements, which consist of a pair of valley-shaped protrusions that are continuously located on the other side and project to the other surface, are formed so that the spacers are located in the central portion of the flat surface on the opposite side of the catalyst elements that are adjacent to each other. In the exhaust gas purification catalyst unit
The upper and lower frame surfaces of the metal frame have gas stirring protrusions composed of linear protrusions protruding toward the catalyst element facing the frame surface, and the gas stirring protrusions are the spacers of the catalyst element. An exhaust gas purification catalyst unit characterized by extending in a direction intersecting the extension direction. In the exhaust gas purification catalyst unit according to claim 1,
The exhaust gas purification catalyst unit characterized in that the gas stirring protrusion is located facing a flat surface between two adjacent spacers of the catalyst element. In the exhaust gas purification catalyst unit according to claim 2.
The layer spacing P ₁ of the catalyst element is a value selected from the range of 4 [mm] to 10 [mm].
The height H of the gas stirring protrusion is a catalyst unit for exhaust gas purification, wherein the value of the ratio of _{H / P 1 is set in the range of 1/3 to 2/3.} In the exhaust gas purification catalyst unit according to claim 3,
A catalyst unit for exhaust gas purification, wherein a plurality of the gas stirring protrusions are provided in the gas flow direction, and the installation interval D is set to a value selected from the range of 20 [mm] to 50 [mm]. In the exhaust gas purification catalyst unit according to claim 4,
The exhaust gas purification catalyst unit is characterized in that the metal frame is made of a rolled steel plate having a thickness of 1 [mm] to 2 [mm]. In the exhaust gas purification catalyst unit according to claim 3,
The height H of the gas agitating protrusion located in the gas flow path surrounded by the spacer and the flat surface adjacent to the catalyst element facing the frame surface of the metal frame has the cross-sectional area of the gas flow path as A. For exhaust gas purification, the S / A ratio is set to a value selected from the range of 20% to 60%, where S is the projected area of the gas stirring protrusion viewed from the gas flow direction. Catalyst unit.

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